The invention relates to a controllable coolant pump, particularly for a coolant circuit of an internal combustion engine. The design of the radial pump comprises a pump housing, in which a pump shaft embodied as a hollow shaft with a corresponding impeller is supported in a rotational fashion. In the operating state coolant is conveyed during the rotation of the impeller via a suction connection into a spiral port of the coolant pump. In order to influence the volume conveyed an axially displaceable guide disk is provided, cooperating with an actuating e mechanism and/or actuators or an adjustment unit and allocated to the impeller, which is connected to a push rod, guided in a rotary fixed manner in the hollow shaft and displaceable between two end positions of a rear wall and a pump cover of the impeller.
In vehicles, preferably water-cooled internal combustion engines have proven effective. Here, in order to cool the internal combustion engine a coolant, particularly cooling water is pumped with the help of a coolant pump in a closed circuit via cooling channels of the engine block and the cylinder head and subsequently guided into an air-water heat exchanger and/or radiator, where the heated coolant is cooled back by airflow or by a fan when the vehicle is stationary. The coolant pump supporting the circulation of the coolant is usually driven directly via a traction drive, particularly a belt drive, with a traction element connecting the belt pulley of the crank shaft to the coolant pump.
This drive between the coolant pump and the crank shaft causes a dependency of the rotation of the pump on the rotation of the internal combustion engine. This leads to the consequence that coolant already circulates during cold starts of the internal combustion engine, which hinders the warm-up of the internal combustion engine, and thus the reaching of an optimal operating temperature as fast as possible is delayed. Due to this fact, controllable coolant pumps are used, in which the volume flow conveyed can be adjusted according to the cooling need of the internal combustion engine. This way, loss by friction can be minimized, because with increasing oil temperature the viscosity of the lubricating oil and consequently the friction is reduced, which has beneficial effects on the fuel consumption. Simultaneously, improved exhaust emissions are yielded, because the effectiveness of the catalytic converter requires a minimum exhaust temperature and a reduced period of time to reaching said temperature has directly positive effects on the exhaust emissions. Vehicle manufacturers request in the cold-operating phase of the internal combustion engine a coolant flow of the coolant pump of ≦0.5 l/h, also called “zero leakage flow”. Under test conditions, fuel savings of ≧2.5% could be realized by the development of internal combustion engines in order to yield an energetically and thermo-mechanically improved operation in connection with an optimal thermal management.
From DE 199 01 123 A1 a measure is known to influence the volume conveyed by a coolant pump, comprising a slider allocated to the open impeller covering the blades of the impeller and influencing the effective width of the blades, which is continuously movable in the axial direction and can be arbitrarily adjusted. The adjustment of the slider between an opening and a closing position occurs here by rotating a thread-like guidance. According to DE 100 57 098 A1 a controllable coolant pump comprises a magnetic coil cooperating with an anchor plate, which is arranged in a rotary fixed but spring-loaded displaceable manner on a drive shaft. When the magnet is not electrified, the drive of the impeller occurs due to the friction coatings, by which the impeller is connected to the anchor plate.
DE 100 2005 004 315 A1 as well as DE 10 2005 062 200 A1 show coolant pumps, in which in order to influence the volume conveyed the pump housing one annularly embodied valve slider is inserted, supported displaceable in the direction of the shaft axis of the pump shaft, which includes an exterior cylinder, for variably covering the outflow area of the impeller. According to DE 10 2005 004 315 A1 the valve slider, also called guide disk, is adjusted electro-magnetically via a magnetic coil arranged in the pump housing. Alternatively, DE 10 2005 062 200 A1 includes an actuator, operated pneumatically or hydraulically, in order to adjust the valve slider.